Reducing comments

.gitea/ci-image/Dockerfile

@@ -1,26 +1,16 @@
-# Custom CI image for the arm64 (Raspberry Pi) Gitea Actions runner.
+# Custom CI image for the arm64 (Raspberry Pi) Gitea Actions runner,
+# since the official sagemath/sagemath image is amd64-only.
 #
-# The official sagemath/sagemath image is amd64-only; conda-forge's `sage`
-# package is the one place SageMath is actually published for linux-aarch64,
-# so this bakes it (plus the lint/test tools) into a single image, built and
-# pushed once rather than reinstalled on every CI run.
-#
-# Build & push (run directly on the Pi, or any arm64 machine with Docker):
+# Build & push commands:
 #   docker build -t gitea.piribauer.ch/julian/sage-ci:latest -f .gitea/ci-image/Dockerfile .
 #   docker login gitea.piribauer.ch -u julian
 #   docker push gitea.piribauer.ch/julian/sage-ci:latest
-#
-# Rebuild and re-push whenever this Dockerfile changes (e.g. bumping the sage
-# version) or the pinned tool versions need updating.
 
 FROM condaforge/miniforge3:latest
 
 RUN mamba install -y -c conda-forge sage ruff pytest \
     && mamba clean -afy
 
-# actions/checkout@v4 (and other JS-based actions) run via `node` inside this
-# container -- act_runner doesn't inject a runtime of its own when a custom
-# `container:` image is set, so one has to be present here.
 RUN mamba install -y -c conda-forge nodejs \
     && mamba clean -afy